When a hooker attempts to steal a wallet from a drunken john, she accidentally makes a horrific discovery — the couple is not alone in a shabby room of a love hotel.

In my mind finding a dead body is a weak inciting incident because it is something she does herself, could have easily avoided and chooses to make something of it rather than just run away after seeing the body.

But if the inciting incident was her being accused of murder. That would be something that is done to her by an external force and she has to take action to fix it. More so presumably being a prostitute her character will be held at doubt and it would be harder for her to convince people of her innocence. So she has a built in obstacle as the MC.

When a down on her luck prostitute discovers an horribly mutilated body under the bed, she and her drunk john must evade the deranged owner of the deserted motel.

>>she discovers a corpse under the bed

That would be the inciting incident -- not the attempt to steal the wallet.

But then what happens? What problem does it create for the hooker (and john)? What must she (I presume the hooker is the main character) do about -- what becomes her objective goal? Who or what opposes her efforts? What's at stake for her? Is she going to be framed? Must she prove her innocence? Or...?

>>she discovers a corpse under the bed

That would be the inciting incident -- not the attempt to steal the wallet.

But then what happens? What problem does it create for the hooker (and john)? What must she (I presume the hooker is the main character) do about -- what becomes her objective goal? Who or what opposes her efforts? What's at stake for her? Is she going to be framed? Must she prove her innocence? Or...?

Those are all good points. I will try to rework it. "Love Hotel" is something that is very common in Asia (the story takes place in Tokyo), and it is a place where people go for a tryst and pay by hour.

Daniel, it would be good if the wallet played such a role, however, that's not what happens. While a customer is taking a shower, the hooker checks his pockets and finds the wallet. He abruptly steps out of the shower catching her in a act. She then throws the wallet under the bed.

It is upon retrieving that wallet that she discovers a corpse under the bed -- that is what's so horrific about it...

What role does the wallet play? For now it seems like stealing it is just something the hooker does when the main problem is presented. If the wallet must be important, maybe you could make it to the antagonist, like for example:

When a hooker tries to steal a wallet from a drunken sex-customer she discovers the wallet is cursed and must defeat it before it kills her.